Ceria nanocrystallites with different morphologies and crystal planes were hydrothermally prepared, and the effects of ceria supports on the physicochemical and catalytic properties of Pd/CeO 2 for the CO and propane oxidation were examined. The results showed that the structure and chemical state of Pd on ceria were affected by ceria crystal planes. The Pd species on CeO 2 -R (rods) and CeO 2 -C (cubes) mainly formed Pd x Ce 1−x O 2−σ solid solution with −Pd 2+ −O 2− −Ce 4+ − linkage. In addition, the PdO x nanoparticles were dominated on the surface of Pd/CeO 2 -O (octahedrons). For the CO oxidation, the Pd/CeO 2 -R catalyst showed the highest catalytic activity among three catalysts, its reaction rate reached 2.07 × 10 −4 mol g Pd −1 s −1 at 50 °C, in which CeO 2 -R mainly exposed the ( 110) and (100) facets with low oxygen vacancy formation energy, strong reducibility, and high surface oxygen mobility. TOF of Pd/CeO 2 -R (3.78 × 10 −2 s −1 ) was much higher than that of Pd/CeO 2 -C (6.40 × 10 −3 s −1 ) and Pd/CeO 2 -O (1.24 × 10 −3 s −1 ) at 50 °C, and its activation energy (E a ) was 40.4 kJ/mol. For propane oxidation, the highest reaction rate (8.08 × 10 −5 mol g Pd −1 s −1 at 300 °C) was obtained over the Pd/CeO 2 -O catalyst, in which CeO 2 -O mainly exposed the (111) facet. There are strong surface Ce−O bonds on the ceria (111) facet, which favors the existence of PdO particles and propane activation. The turnover frequency (TOF) of the Pd/CeO 2 -O catalyst was highest (3.52 × 10 −2 s −1 ) at 300 °C and its E a value was 49.1 kJ/mol. These results demonstrate the inverse facet sensitivity of ceria for the CO and propane oxidation over Pd/ ceria.

Sm-Mn mixed oxide catalysts prepared by the coprecipitation method were developed, and their catalytic activities were tested for the selective catalytic reduction (SCR) of NO with ammonia at low temperature. The results showed that the amount of Sm markedly influenced the activity of the MnO x catalyst for SCR, that the activity of the Sm-Mn mixed oxide catalyst exhibited a volcano-type tendency with an increase in the Sm content, and that the appropriate mole ratio of Sm to Mn in the catalyst was 0.1. In addition, the presence of Sm in the MnO x catalyst can obviously enhance both water and sulfur dioxide resistances. The effect of Sm on the physiochemical properties of the Sm-MnO x catalyst were investigated by XRD, low-temperature N2 adsorption, XPS, and FE-SEM techniques. The results showed that the presence of Sm in the Sm-MnO x catalyst can restrain the crystallization of MnO x and increase its surface area and the relative content of both Mn4+ and surface oxygen (OS) on the surface of the Sm-MnO x catalyst. NH3-TPD, NO-TPD, and in situ DRIFT techniques were used to investigate the absorption of NH3 and NO on the Sm-MnO x catalyst and their surface reactions. The results revealed that the presence of Sm in the Sm0.1-MnO x catalyst can increase the absorption amount of NH3 and NO on the catalyst and does not vary the SCR reaction mechanism over the MnO x catalyst: that is, the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms (bidentate nitrate is the active intermediate), in which the Eley–Rideal mechanism is predominant.

The doping of In2O3 significantly promoted the catalytic performance of Co3O4 for CO oxidation. The activities of In2O3–Co3O4 increased with an increase in In2O3 content, in the form of a volcano curve. Twenty-five wt % In2O3–Co3O4 (25 InCo) showed the highest CO oxidation activity, which could completely convert CO to CO2 at a temperature as low as −105 °C, whereas it was only −40 °C over pure Co3O4. The doping of In2O3 induced the expansion of the unit cell and structural distortion of Co3O4, which was confirmed by the slight elongation of the Co–O bond obtained from EXAFS data. The red shift of the UV–vis absorption illustrated that the electron transfer from O2– to Co3+/Co2+ became easier and implied that the bond strength of Co–O was weakened, which promoted the activation of oxygen. Low-temperature H2-TPR and O2-TPD results also revealed that In2O3–Co3O4 behaved with excellent redox ability. The XANES, XPS, XPS valence band, and FT-IR data exhibited that the CO adsorption strength became weaker due to the downshift of the d-band center, which correspondingly weakened the adsorption of CO2 and obviously inhibited the accumulation of surface carbonate species. In short, the doping of In2O3 induced the structural defects, modified the surface electronic structure, and promoted the redox ability of Co3O4, which tuned the adsorption strength of CO and oxygen activation simultaneously.

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Ruthenium (Ru) nanoparticles (∼3 nm) with mass loading ranging from 1.5 to 3.2 wt % are supported on a reducible substrate, cerium dioxide (CeO, the resultant sample is called Ru/CeO), for application in the catalytic combustion of propane. Because of the unique electronic configuration of CeO, a strong metal-support interaction is generated between the Ru nanoparticles and CeO to stabilize Ru nanoparticles for oxidation reactions well. In addition, the CeO host with high oxygen storage capacity can provide an abundance of active oxygen for redox reactions and thus greatly increases the rates of oxidation reactions or even modifies the redox steps. As a result of such advantages, a remarkably high performance in the total oxidation of propane at low temperature is achieved on Ru/CeO. This work exemplifies a promising strategy for developing robust supported catalysts for short-chain volatile organic compound removal.